Timer interrupt never hits TIMER0_IRQHandler with LPC1769 LPCXpresso

Question

I have LPC1769 LPCXpresso and LPC-Link 2 for debugging. My development environment is IAR.

I wanted to experience a simple LED blinking using Timer. There are many sample codes on the net. So, I picked one of the samples made for MCB1700 board. I have also read some here and there how timer works with LPC's.

The code compiles and I downloaded the program to the device (LPC1769). I was assuming the LED should blink when the timer calls the handler by the given interval.

But, the program never hits TIMER0_IRQHandler at all.

Here is the complete code in my main.c file:

#include 

void TIMER0_IRQHandler(void);

int main(void) 
{
  // (1) Timer 0 configuration (see page 490 of user manual)
  LPC_SC->PCONP |= 1 << 1; // Power up Timer 0 (see page 63 of user manual)
  LPC_SC->PCLKSEL0 |= 1 << 2; // Clock for timer = CCLK, i.e., CPU Clock (page 56 user manual)
  // MR0 is "Match Register 0". MR0 can be enabled through the MCR to reset
  // the Timer/Counter (TC), stop both the TC and PC, and/or generate an interrupt
  // every time MR0 matches the TC. (see page 492 and 496 of user manual)

  LPC_TIM0->MR0 = 500; //Toggle Time in mS
  //LPC_TIM0->MR0 = 1 << 23; // Give a value suitable for the LED blinking

  // frequency based on the clock frequency
  // MCR is "Match Control Register". The MCR is used to control if an
  // interrupt is generated and if the TC is reset when a Match occurs.
  // (see page 492 and 496 of user manual)
  LPC_TIM0->MCR |= 1 << 0; // Interrupt on Match 0 compare
  LPC_TIM0->MCR |= 1 << 1; // Reset timer on Match 0
  // TCR is "Timer Control Register". The TCR is used to control the Timer
  // Counter functions. The Timer Counter can be disabled or reset
  // through the TCR. (see page 492 and 494 of user manual)
  LPC_TIM0->TCR |= 1 << 1; // Manually Reset Timer 0 (forced);
  LPC_TIM0->TCR &= ~(1 << 1); // Stop resetting the timer
  // (2) Enable timer interrupt;
  // TIMER0_IRQn is 1, see lpc17xx.h and page 73 of user manual
  NVIC_EnableIRQ(TIMER0_IRQn); // see core_cm3.h header file
  // (3) Some more one-time set-up's;
  LPC_TIM0->TCR |= 1 << 0; // Start timer (see page 492 and 494 of user manual)
  LPC_SC->PCONP |= ( 1 << 15 ); // Power up GPIO (see lab1)
  LPC_GPIO1->FIODIR |= 1 << 29; // Put P1.29 into output mode. LED is connected to P1.29
  // (4) infinite loop;
  while (1) // Why do we need this?
  {
    //LPC_GPIO1->FIOPIN ^= 1 << 29; // Toggle the LED (see lab1)
  }
  return 0;
}


// Here, we describe what should be done when the interrupt on Timer 0 is handled;
// We do that by writing this function, whose address is “recorded” in the vector table
// from file startup_LPC17xx.s under the name TIMER0_IRQHandler;
void TIMER0_IRQHandler(void)
{
  // IR is "Interrupt Register". The IR can be written to clear interrupts. The IR
  // can be read to identify which of eight possible interrupt sources are
  // pending. (see page 492 and 493 of user manual)
  if ( (LPC_TIM0->IR & 0x01) == 0x01 ) // if MR0 interrupt (this is a sanity check);
  {
    LPC_TIM0->IR |= 1 << 0; // Clear MR0 interrupt flag (see page 492 and 493 of user manual)
    LPC_GPIO1->FIOPIN ^= 1 << 29; // Toggle the LED (see lab1)
  }
}

Any pointer would be greatly appreciated.

[EDIT]

For future reference for whom has the similar question, here is my working code;

I have re-written with knowledge I gathered from here and there. Now it works, all handlers are triggered. This time I wanted to test with multiple Timers. Here is the implementation with two Timer-IRQ's and SysTick.

#include "LPC17xx.h"

#define SBIT_TIMER0  1
#define SBIT_TIMER1  2

#define SBIT_MR0I    0
#define SBIT_MR0R    1

#define SBIT_CNTEN   0

#define PCLK_TIMER0  2
#define PCLK_TIMER1  4    

#define LED1         0 // P2_0
#define LED2         1 // P2_1

#define MiliToMicroSec(x)  (x*1000)  /* ms is multiplied by 1000 to get us*/

extern unsigned int SystemCoreClock;
unsigned int getPrescalarForUs(uint8_t timerPclkBit);

static int data_main = 0;
static int data_systick = 0;

void Delay(uint32_t Dly)
{
   for(volatile uint32_t j = Dly; j; j--) { }
}

void SysTick_Handler(void)
{
   data_systick += 10;
}

int main (void) 
{
    SystemInit();

    LPC_SC->PCONP |= (1<MCR  = (1<PR   = getPrescalarForUs(PCLK_TIMER0);      /* Prescalar for 1us */
    LPC_TIM0->MR0  = MiliToMicroSec(100);                 /* Load timer value to generate 100ms delay*/
    LPC_TIM0->TCR  = (1 <MCR  = (1<PR   = getPrescalarForUs(PCLK_TIMER1);      /* Prescalar for 1us */
    LPC_TIM1->MR0  = MiliToMicroSec(500);                 /* Load timer value to generate 500ms delay*/
    LPC_TIM1->TCR  = (1 <FIODIR = (1<IR; 
    LPC_TIM0->IR = isrMask;         /* Clear the Interrupt Bit */

    LPC_GPIO2->FIOPIN ^= (1<IR;
    LPC_TIM1->IR = isrMask;        /* Clear the Interrupt Bit */

    LPC_GPIO2->FIOPIN ^= (1<PCLKSEL0 >> timerPclkBit) & 0x03;  /* get the pclk info for required timer */

    switch ( pclk )                                    /* Decode the bits to determine the pclk*/
    {
    case 0x00:
        pclk = SystemCoreClock/4;
        break;

    case 0x01:
        pclk = SystemCoreClock;
        break; 

    case 0x02:
        pclk = SystemCoreClock/2;
        break; 

    case 0x03:
        pclk = SystemCoreClock/8;
        break;

    default:
        pclk = SystemCoreClock/4;
        break;  
    }

    prescalarForUs =pclk/1000000 - 1;                    /* Prescalar for 1us (1000000Counts/sec) */

    return prescalarForUs;
}

Timer interrupt never hits TIMER0_IRQHandler with LPC1769 LPCXpresso

Answers (1)

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